A fun little trick for getting all the mayo out of the block after you've got it all together :
1. After final assembly, fill the sump with three quarts of the cheapest oil you can buy. The 99p per quart stuff. Add one quart of automatic transmission fluid. Stick on an absolute dirt cheap oil filter.
2. Fire the engine up for about 2-3 minutes. Just enough to circulate the ATF around every nook and cranny of the engine. The ATF will suspend EVERY little bit of water in the engine in itself and trap it all in the oil filter.
3. Do a complete oil change using a repeat of step one and two. Verify at the end that there is no more mayo (or at the most only a hint) in the oil. If there's still quite a bit, do another change. Even 1cc of water will completely contaminate four quarts of the best oil on the market and make it useless to your engine.
4. When there's no more hint of mayo in what's coming out the sump plug, put your favorite oil and a good filter on and you're ready to go.